Great-depth-of-field (G.D.F.) telescopes as described in U.S. Pat. No. 5,189,560 have proven to be useful. Although they do function satisfactorily, there are inherent limitations experienced by certain individuals when using these miniature scopes. These limitations include lowered luminosity levels, relatively small fields-of-view, and restricted eye crystalline lens accommodation capabilities. Eye lens non-accommodation can be medically termed presbyopia. Presbyopia is very common especially in the middle-aged and older citizenry. This condition results from the eye lens no longer being able to observe a clear great-depth-of-field when relaxed.
In addition, conditions resulting from eyeball shape irregularities such as myopia, hyperoptic and astigmatism in combination with presbyopia further limit a user's ability to visually realize the great-depth-of-field offered by these scopes. Scope users with more perfect visual capabilities do not experience such limitations. The most perfect visual capability is medically termed emmotropic. Here, the eye displays neither nearsightedness (myopia), farsightedness (hyperopic), astigmatism, nor eye lens accommodation difficulties (presbyopia).
The principal hindrance experienced by many G.D.F. scope users is that of not being able to perceive visually the entire depth-of-field that the U.S. Pat. No. 5,189,560 scopes offer. The clear ocular end of the scope field-depth zone is seen while the far or objective end of the field-depth zone offered by these scopes is unclear to some degree.
For other individual scope users the reverse might be true. Corrective spectacle or contact lenses might help to improve, to some small degree, these eye dysfunctions when using these Edward's et. al. G.D.F. scopes. (U.S. Pat. No. 5,189,560)